This invention relates to an elastically stretchable composite sheet and a process for making the same.
Japanese Patent Application (PCT) Publication No. 1996-504693A describes a multilayered elastic panel and a process for making the same. This elastic layer comprises a rubber elastic layer and an inelastic fibrous layer bonded to the former in bonding zones so that the inelastic fibrous layer forms gathers between each pair of the adjacent bonding zones. The inelastic fibrous layer is formed with fibers obtained with spun bonding process or melt blown process.
While it is possible for the prior art to obtain fine fibers having a fineness less than 0.1 dtex using the melt blown process, it is difficult for the prior art to control a cross-section presented by each of these fibers in a predetermined shape. This process is thus unsuitable for improvement of fiber surface luster by flattening the cross-sectional shape of the fiber. In addition to this, it is impossible for this process to use the nozzles each having a relatively large diameter and therefore it is difficult for this process to increase discharge from each nozzle per unit time and thereby to improve a productivity of the fiber. While such drawback of the melt blown process may be eliminated by use of the spun bonding process, it is difficult for this spun bonding process to obtain fine fibers of a fineness less than 1 dtex at a high efficiency and therefore it is difficult for this process to obtain comfortably flexible fibrous layer offered by the fibers of adequately low fineness.
It is an object of this invention to eliminate the drawbacks involved in the composite sheet comprising the elastically stretchable layer and the inelastically stretchable fibrous layer and the process for making the same, for example, as disclosed in the Publication.
According to a first aspect of this invention, there is provided an elastically stretchable composite sheet and, according to a second aspect of this invention, there is provided a process for making the composite sheet.
The first aspect of this invention relates to an elastically stretchable composite sheet comprising a first web having x- and y-directions orthogonal to each other and being elastically stretchable at least in the y-direction and a second web made of thermoplastic synthetic resin fibers and being inelastically stretchable in the y-direction, the first and second webs being bonded to each other in bonding zones intermittently arranged in the y-direction wherein a length of the thermoplastic synthetic resin fiber bonded to the first web measured between each pair of the adjacent bonding zones is longer than a straight distance defined between the pair of the adjacent bonding zones.
The improvement according to this invention in the composite sheet is in that the fiber has in its cross-section cut in a direction orthogonal to its longitudinal direction a width w and a height h orthogonal to the width w dimensioned so that a ratio of h/w is less than 0.5.
The second aspect of this invention relates to a process for making an elastically stretchable composite sheet comprising first web having x- and y-directions orthogonal to each other and being elastically stretchable at least in the y-direction and second web made of a plurality of thermoplastic synthetic resin fibers and being inelastically stretchable in the y-direction, the first and second webs being bonded to each other in bonding zones intermittently arranged in the y-direction wherein a length of the thermoplastic synthetic resin fiber bonded to the first web measured between each pair of the adjacent bonding zones is longer than a straight distance defined between the pair of the adjacent bonding zones.
The improvement according to the second aspect of this invention in the process for making the composite sheet comprising the steps of:
a. continuously feeding the first web in the y-direction;
b. obtaining conjugated fibers each comprising at least two types of thermoplastic synthetic resin and being dividable into the at least two types of resin by melt spinning and then continuously feeding an assembly of the conjugated fibers in the form of web in the y-direction for said second web;
c. placing the first web and the web of conjugated fibers for said second web upon each other and bonding these two webs together in bonding zones arranged intermittently in the y-direction to form a composite web;
d. stretching the composite web in the y-direction and obtaining the second web from the web of conjugated fibers; and
e. contracting the stretched composite web to obtain the composite sheet.
According to one preferred embodiment of this invention, further comprising a step of continuously feeding the composite web in stretched or contracted state and subjecting the conjugated fibers to high pressure columnar water streams discharged from a plurality of nozzles to divide each of the conjugated fibers.